1. Technical Field of the Invention
The present invention relates to an apparatus for computing the degree of load applied to a vehicle such as a track, and an apparatus for computing a carrying weight.
2. Explanation of the Prior Art
The carrying weight of a vehicle has been measured for mainly a large-scale vehicle such as a track in Japan in order to prevent the traffic accident such as turn-over on its side due to excessive carrying and promotion of vehicle deterioration.
Conventionally, the carrying weight of a vehicle has been measured with an object to be measured on a scale. However, the facilities used requires a large scale and so a wide installing space, thereby limiting the number of scales which can be installed. This does not permit measurement to be made for a larger number of vehicles and increases the installation cost.
Therefore, in recent years, a carrying weight computing apparatus in which the weight on board of the vehicle itself is computed has been proposed.
In the conventional vehicle on-board type weight computing apparatus, a sensing element for weight measurement such as a distortion gauge sensor is attached to each of arc leaf springs, which are arranged between the front/rear and left/right positions of a platform frame and left/right ends of both front and rear axle. The carrying weight is computed by totaling the outputs from the sensing elements in proportion to the loads applied to the respective sensing elements.
However, the outputs from the sensing elements change as the deflection of load applied to a vehicle, particularly, the deflection of load in a vehicle width direction, changes according to whether or not the vehicle stays on an inclined ground, to carrying balance of load in a platform and to the characteristic of distribution of weight of a vehicle itself.
Therefore, only totaling the measured values of the above sensing elements may not compute a collect carrying weight. Thus, in order to improve the computing accuracy, the presence or absence of the deflection of loading or its contents must be taken in consideration.
In the sensing element such as a distortion gauge sensor, the characteristic when the load applied to it increases is not coincident to that when the load decreases. Specifically, the sensing element has a non-linear characteristic inclusive of the hysterisis in which a higher output when the load increases is provided than that when it decreases.
In addition, there is a variation in the characteristic among a plurality of sensing elements used for computing the deflection of load or carrying weight.
For this reason, if the deflection of load is simply computed on the basis of the outputs from the sensing elements under the judgment that the variation in the outputs from the sensing elements is due to the deflection of the load, the influence of hysterisis and a variation of the characteristics among the sensing elements is left as it is within the deflection or carrying weight. Therefore, on the way where the load applied to the vehicle decreases, the output from the sensing element becomes a negative load value. Thus, on the basis of the output value, correct deflection or carrying weight cannot be computed.
Further, the output from each sensing element varies when a vehicle vibrates owing to its running. Therefore, in order to compute the carrying weight accurately, the state of running or stopping of the vehicle is preferably taken in consideration.